Conventionally, there are known to be various techniques for deinterlacing an image, or in other words, for converting an interlaced image into a progressive image. As is widely known, an interlaced image is an image that is a combination of a top field image (an odd-numbered row image in the case of numbering from an odd-numbered first row, and an even-numbered row image in the case of numbering from an even-numbered first row) and a bottom field image (an even-numbered row image in the case of numbering from an odd-numbered first row, and an odd-numbered row image in the case of numbering from an even-numbered first row) that were captured at different times. Due to this time difference, the same subject appearing in an interlaced image is horizontally shifted alternately between the odd-numbered rows and the even-numbered rows, and as a result, a horizontal stripe pattern called interlace striping tends to appear.
Since this interlace striping appears as jaggedness and flickering to the human eye, it is often the situation that deinterlacing is desired when interlaced images are handled as still images, for example. Patent Literature 1 (JP 2010-141717A) is related to an apparatus for capturing a still image from a moving image, this apparatus automatically determines whether or not frames to be captured are interlaced images, and automatically deinterlaces frames that were determined to be interlaced images.
However, in order to determine whether or not frames are interlaced images, the apparatus in Patent Literature 1 references a predetermined flag recorded in association with each frame in a predetermined data area in the moving image data. This flag uses “0” and “1” to indicate whether or not the frames in the moving image data are interlaced images or progressive images, and is metadata that is multiplexed with the data body of the frames in the moving image data.
Accordingly, with the apparatus of Patent Literature 1, the automatic determination of whether or not a frame is an interlaced image cannot be performed on frames in moving image data that does not have the above-described flag recorded therein. Furthermore, the data area in which the above-described flag is recorded in the moving image data is determined according to the algorithm used by the encoder that compressed the moving image data. Accordingly, even if the above-described flag is recorded in the moving image data, it cannot be referenced unless the algorithm that was used by the encoder is known. In other words, the apparatus in Patent Literature 1 cannot correctly determine whether or not a frame is an interlaced image with frames in any data format, and there is a limit to the number of data formats with which it is possible to correctly determine whether or not a frame is an interlaced image.